Been at this for days, I have very successfully imported STL files, converted to solids by merging faces and added holes and counterbores in the past. But this file has stumped me. Its part of a clock I want to 3D print but the piece is too big for my printer so I cut it roughly in half with my slicer and wanted to add a few 2mm blind holes to a few faces to "dowel" the two haves when I glue them together. I have reduced the mesh slices to reduce the file size and can import. When I convert to solid, all I get is a wireframe display and can't select any flat surfaces to sketch on to pull a small hole. I have attached the Designspark file and the offending STL. Any help is appreciated.